WASHINGTON – The former longtime clerk of the House faces investigators today in possibly the most important testimony yet on how GOP leaders dealt with allegations about then-Rep. Mark Foley's behavior toward male pages. That includes the Republicans' secret handling last fall of a complaint to a Louisiana congressman who testified yesterday.

The questioning of former House Clerk Jeff Trandahl is coming after Rep. Rodney Alexander, R-La., spent three hours with ethics investigators

Alexander sought to explain how his office dealt with the complaint from a former page about overly friendly e-mails from Foley. Afterward, he said he told the panel “what we know, when we knew it and what we did about it.”

“It's quite apparent from some of the reports out there that there are many people that know what we've known, and have known it for a lot longer period of time than we've known it,” Alexander said.

GOP leaders are facing scrutiny over whether they or their aides did too little to stop Foley's interactions with pages when problems surfaced years ago. The revelations have been followed by weakening poll numbers for Republicans, who insist that no one in their party knew of the sexually graphic electronic messages that have caused a scandal.

Trandahl's testimony is critical in determining how many people knew about Foley's behavior and whether there were more incidents than those reported so far.

Alexander discussed the matter last spring with two top GOP lawmakers, Majority Leader John Boehner of Ohio and Tom Reynolds of New York, chairman of the Republican re-election committee in the House, both of whom say they spoke with Speaker Dennis Hastert about it. Hastert has said he did not recall the conversations.

Trandahl confronted Foley last fall over his e-mails to the Louisiana teenager and was alerted about inappropriate electronic messages Foley sent in 2001 or 2002 to a former page sponsored by Rep. Jim Kolbe, R-Ariz.

As the House officer with responsibility for the page program, Trandahl was in the position to know whether there were other complaints about Foley, including an alleged incident in which the Florida Republican tried to enter the Capitol Hill dorm for pages in 2003 while drunk.

The panel is trying to determine whether lawmakers and aides acted properly when alerted about Foley's behavior. Trandahl's testimony is crucial to knowing how many people knew about the page issue – and how problems with Foley were handled – before ABC News reported on the e-mails last month.

Foley resigned Sept. 29 after being confronted with sexually explicit messages sent in 2003 to a former Oklahoma page.

Kirk Fordham, Foley's former chief of staff, told the ethics panel that he informed top House GOP aides of Foley's questionable behavior toward pages years ago. Fordham has testified he told senior House staff aides about the dorm incident.

A key issue is whether staff aides to Hastert knew about Foley's interactions with pages before the complaint from the Louisiana boy last year and whether they told Hastert – who says he knew nothing about Foley and pages prior to the day Foley resigned.

Yesterday, Foley's most recent chief of staff, Elizabeth Nicolson, testified before the ethics panel. She has told former associates that she was unaware of Foley's behavior.

On Tuesday, House Sergeant-at-Arms Wilson Livingood, a member of the Page Board, which oversees the program for high school students, was questioned for less than two hours. He did not comment afterward.

The ethics panel also heard Tuesday from Paula Nowakowski, chief of staff to Boehner.

Alexander sponsored a page who complained of receiving overly friendly e-mails from Foley, including one that asked for a photograph and mentioned a different boy who was in “great shape.”

Alexander's aide last fall told Hastert's aide about the e-mails, setting off a chain of events that led Trandahl and Page Board Chairman John Shimkus, R-Ill., to tell Foley to stop contacting the teenager.

Boehner, whom Alexander subsequently alerted about the e-mails last spring, also is expected to testify today. Boehner's public statements are at odds with Hastert's. Boehner told a Cincinnati radio station earlier this month that when he approached Hastert about Foley last spring, Hastert told him “it had been taken care of.”

Hastert and his aides, including his chief of staff Scott Palmer, have yet to testify before the panel.